1,721,094 research outputs found
Formulation and release behavior of doxycycline- alginate complex hydrogel microparticles embedded into Pluronic F127 thermogels for doxycycline intradermal sustained delivery
No full textPurpose. The aim of this work was the formulation and characterization of a new doxycycline (Dox)- alginate complex hydrogel microparticles embedded into Pluronic F127 thermogel for doxycycline intradermal sustained delivery.
Methods. Batches of Dox-Alginate complex MP were prepared by direct injection of a solution of the drug into a 1.5% polymer solution upon silverson stirring. The MP were recovered and freeze-dried. The hydrogel MP were successively formed by dispersing the MP into a 1.2% CaCl2 solution. The MP were characterized in terms of size, drug content, and release behavior by HPLC. Free Dox and hydrogel MP were then embedded into PF127, PF127-HPMC, and PF127-Methocel thermogels. The thermogels were produced by dissolving PF127 and HPMC or Methocel in phosphate buffer at 4°C and were characterized in terms of gelling time, morphology and release behavior. A target release period of 6-7 days was considered optimal.
Results. Dox-Alginate complexation occurred spontaneously either in water or phosphate buffer upon mixing. The hydrogel MP were about 20 μm in size with 90% of the population < 59 μm. Drug content was about 35% w/w for all the preparations. Dox was released fast from the MP with a 90% after just 1-2 days. An expected faster release was also observed for free Dox from the thermogels with 80-90% of drug released after 3.5-4 hours, even in the presence of 1% HPMC or Methocel. The release was much slower and sustained after embedding the MP into PF127 and PF127-HPMC thermogels. In particular, the PF127-HPMC thermogel showed an almost linear release reaching 80% after 3 days and 90% up to 6 days.
Conclusions. Although a further characterization and formulation assessment is needed to optimize MP characteristics, Dox-Alginate loaded hydrogel MP, when embedded into a PF127-HPMC thermogel, seem to be promising in order to achieve a 7 days sustained release formulation for Dox intradermal sustained delivery
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Effect of water on the physical and chemical properties of end-capped poly(d,l-lactide-co-glycolide)
Full text linkA Short Term Quality Control Tool for Biodegradable Microspheres
No full textAccelerated in vitro release testing methodology has been developed as an indicator of product performance to be used as a discriminatory quality control (QC) technique for the release of clinical and commercial batches of biodegradable microspheres. While product performance of biodegradable microspheres can be verified by in vivo and/or in vitro experiments, such evaluation can be particularly challenging because of slow polymer degradation, resulting in extended study times, labor, and expense. Three batches of Leuprolide poly(lactic-co-glycolic acid) (PLGA) microspheres having varying morphology (process variants having different particle size and specific surface area) were manufactured by the solvent extraction/evaporation technique. Tests involving in vitro release, polymer degradation and hydration of the microspheres were performed on the three batches at 55°C. In vitro peptide release at 55°C was analyzed using a previously derived modification of the Weibull function termed the modified Weibull equation (MWE). Experimental observations and data analysis confirm excellent reproducibility studies within and between batches of the microsphere formulations demonstrating the predictability of the accelerated experiments at 55°C. The accelerated test method was also successfully able to distinguish the in vitro product performance between the three batches having varying morphology (process variants), indicating that it is a suitable QC tool to discriminate product or process variants in clinical or commercial batches of microspheres. Additionally, data analysis utilized the MWE to further quantify the differences obtained from the accelerated in vitro product performance test between process variants, thereby enhancing the discriminatory power of the accelerated methodology at 55°C. © 2014 American Association of Pharmaceutical Scientists
Effect of agitation regimen on the in vitro release of leuprolide from PLGA microparticles
No full textDue to the importance of in vitro release tests in establishing batch-to-batch reproducibility and in vitro/in vivo correlation, this study investigated the influence of the agitation regimen on the in vitro release behavior of leuprolide from PLGA microparticles. Leuprolide loaded microspheres were prepared using Resomer® RG502H and RG503H as polymers. Leuprolide in vitro release was performed in phosphate buffer solution under continuous or once-a-week agitation. At predetermined intervals, leuprolide release, polymer mass loss (ML), and degree of hydration (DH) were investigated. Leuprolide release and ML were higher under continuous agitation with respect to that under intermittent agitation. Using a modified version of Koizumi equation, it was possible to fit leuprolide release profiles. f2 comparison showed a high level of similarity between experimental and modeled data in the case of once-a-week agitation regimen. This work highlights the importance of the in vitro release conditions on peptide release behavior from polyester microparticles
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